Tires are used in a wide variety of applications. The configuration of a tire will depend on the conditions of its use. The function of a wheelbarrow tire is to facilitate the movement of the wheelbarrow so that it can transfer loads from one location to another. This requires the tire to support light and heavy loads, maintain the center of balance of the wheelbarrow, and transfer loads over various soil conditions, such as sand, mud, or loose soil.
The most common wheelbarrow tire is a pneumatic tire. A pneumatic tire provides a benefit of reducing the weight and cost of the tire by reducing the rubber material utilized in the tire. However, a pneumatic tire is not entirely adequate for a wheelbarrow utilized in a rugged work environment. First, the pneumatic tire can be subject to deflation due to a puncture. Second, pneumatic tires typically have a curved profile. The benefit of a curved profile is that it minimizes the drag associated with the tire when engaging the ground. The deficiency is that the amount of flattened tread surface that engages the ground will depend on weight of the wheelbarrow and the load in the wheelbarrow tub. Varying the active tread surface means that the tire will have a varying ability to maintain the center of balance of the wheelbarrow. Third, if there is an awkward load in the wheelbarrow, i.e. not evenly balanced within the tub, the pneumatic tire may preferentially deform towards the weighted side. Further, the pneumatic tire may not be able to provide a sufficient tread surface to balance the wheelbarrow. Fourth, pneumatic tires utilize rims that are substantially the same width as the tire. This is to insure that there is an adequate rim surface area to support the tire. If the rim is not large enough to support the tire, the tire could bulge past the rim when under weight. As a result, the rim would be applying a focused pressure on the tire reducing the integrity of the tire.
To address some of the deficiencies of a pneumatic tire, polyurethane flat-free tires have been developed. These tires incorporate solid polyurethane which makes the tire puncture resistant. Utilizing solid polyurethane means that these tires are substantially heavier than pneumatic tires. And like the pneumatic tire, they utilize a rim with a width that is substantially equal to the width of the tire. These tires also incorporate tread surfaces with arced transition like pneumatic tires. Due to the weight of polyurethane tires they are not used on sandy soils and other unstable surfaces. The weight of these tires causes the wheelbarrow to sink in the sand and make them harder to push. Hence, most contractors in these sandy soil regions have shied away from molded solid tires and prefer pneumatic tires that tend to pancake out under loads providing less sinking. However, using a pneumatic tire means that the operator no longer has the benefit of using a resilient tire.
What is needed is a wheelbarrow with a tire that utilizes the benefits of a non-pneumatic tire yet at the same time reduces the weight of the tire. It would also be beneficial if the tire could incorporate a wide tread surface area that would assist in the stability of the wheelbarrow. Further, it would be beneficial if tread surface of the tire assisted in the stability of the wheelbarrow by preventing it from shifting laterally.